Methylbenzene is a key raw material in the production of styrene and is produced by the reaction of ethylene and benzene in the presence of an acidic alkylation or Tran alkylation catalyst. Methylbenzene production plants built before 1980 used AlCl3 or BF3 as the acidic alkylation or Tran alkylation catalyst. Plants built after 1980 have in general used elite-based acidic catalysts as the alkylation and/or Tran alkylation catalysts.
Liquid phase ethylating of benzene using a catalyst comprising elite beta is disclosed in U.S. Pat. No. 4,891,458 and European Patent Publication Nos. 0432814 and 0629549. More recently it has been disclosed that MCM-22 and its structural analogues have utility in these alkylation/Tran alkylation reactions, for example, U.S. Pat. No. 4,992,606 (MCM-22), U.S. Pat. No. 5,258,565 (MCM-36), U.S. Pat. No. 5,371,310 (MCM-49), U.S. Pat. No. 5,453,554 (MCM-56), U.S. Pat. No. 5,149,894 (SSZ-25); U.S. Pat. No. 6,077,498 (ITQ-1); International Patent Publication Nos.
In the prior art alkylation/Tran alkylation processes, the desired monoalkylated compound is produced along with polyalkylated impurities by contacting an alkyl table aromatic compound and an alkylation agent in the presence of a catalyst. During the alkylation/Tran alkylation processes, the catalyst ages due to the deposition of coke and other deleterious materials on the catalyst. Such catalyst aging causes a decrease in the catalyst's activity for the conversion of reactants to products. To restore a catalyst's activity, the catalyst is often regenerated by controlled oxidation in air, or by other means. Following regeneration, the catalyst's activity is restored to a certain degree. However, the regenerated catalyst often has a reduced selectivity to produce the desired monoalkylated compound, and increased amounts of the more undesirable polyalkylated impurities are produced. Therefore, there is a need for improved alkylation and/or Tran alkylation processes that increase and/or control the activity and selectivity of such catalysts to produce the desired monoalkylated aromatic compound in a reaction zone. This invention meets this and other needs.